Electrically powered fans used in computer and electronic equipment produce acoustic noise that users find objectionable or annoying. One prominent type of acoustic noise is generated by commutation events that cause torque modulation of a DC brushless fan rotor. The commutation event comprises switching a DC source voltage between windings of the fan. This results in each winding being driven by essentially square current waveforms with an impulse-like profile. The very rapid rise and fall rates of the square current waveform applied to the fan windings cause a torque modulation of the fan rotor. The commutation events are continuously generated while the fan is being driven and are characterized by an acoustic buzzing sound emitted from the fan. The acoustic noise is most noticeable at low fan rotations but is present at all fan speeds.